Fluorescence study of the influence of centrifugation on graphene oxide dispersions in water and in tannic acid.

<br>The potential of tannic acid (TA) as a dispersant for graphene oxide (GO) in water has been investigated for the first time. Transmission electron microscopy (TEM) was used to visualize the degree of GO exfoliation in the dispersions. To further assess TA dispersant capability, a fluorescent biomolecule, riboflavin, has been selected. GO and TA cause a quenching effect on riboflavin fluorescence, which depends on the GO and TA concentration, the GO/TA weight ratio and the final centrifugation step that was found to be crucial. Multiple regression analysis has been used to determine the quenching constants for TA and GO simultaneously. The GO-riboflavin interaction weakens upon centrifugation. This step, traditionally used to remove the nanomaterial aggregates, should be avoided to obtain a high GO concentration in the dispersions. This study paves the way towards the use of green dispersing agents to replace conventional organic solvents or synthetic surfactants to attain high-quality dispersions of carbon nanomaterials in water for numerous applications including biomedicine.